G. Johnstone Stoney.html



George Johnstone Stoney (15 February 1826 – 5 July 1911) was an Irish physicist most famous for introducing the term electron as the "fundamental unit quantity of electricity".¹ He had introduced the concept, though not the word, as early as 1874 and 1881, and the word came in 1891.²³⁴ He published around seventy-five scientific papers during his lifetime.

Life Background

Stoney was born on 15 February 1826 at Oak Park, near Birr, County Offaly, in the Irish midlands. His family was an old-established Anglo-Irish family who had lost their land at the time of the Great Famine.⁵ He attended Trinity College, Dublin, graduating with a B.A. in 1848 and an M.A. in 1852. In 1848 he became the first regular Astronomical Assistant to William Parsons, 3rd Earl of Rosse at Birr Castle, County Offaly, where Parsons had built the world's largest telescope, the 72-inch Leviathan of Parsonstown.

In 1852, Stoney became Professor of Natural Philosophy at Queen's College Galway (now the National University of Ireland, Galway). In 1857, he moved to Dublin as Secretary of the Queen's University of Ireland. He was based in Dublin Castle. While in Dublin he was honorary secretary to the Royal Dublin Society for over 20 years, and then served as a vice-president. He was able to continue his scientific and academic work in close association with this society. He subsequently became superintendent of Civil Service Examinations in Ireland, a post he held until his retirement in 1893. In that year, for family reasons, he took up residence in London. Stoney died on 5 July 1911 at his home in Notting Hill, London.¹

Scientific Work

Stoney published seventy-five scientific papers in a variety of journals, making significant contributions to cosmic physics and to the theory of gases. He estimated the number of molecules in a cubic millimetre of gas, at room temperature and pressure, from data obtained from the kinetic theory of gases. Stoney's most important scientific work was the conception and calculation of the magnitude of the "atom of electricity". In 1891, he proposed the term 'electron' to describe the fundamental unit of electrical charge, and his contributions to research in this area laid the foundations for the eventual discovery of the particle by J.J. Thomson in 1897.

The Stoney Scale

Contemporary physics has settled on the Planck scale as the most suitable scale for a unified theory. The Planck scale was however anticipated by George Stoney.⁶ Like Planck after him, Stoney realized that large-scale effects such as gravity and small-scale effects such as electromagnetism naturally imply an intermediate scale where physical differences might be rationalized. This intermediate scale comprises units (Stoney units)) of mass, length, time etc., yet mass is the cornerstone.

The Stoney mass (expressed in contemporary terms):

where ε₀ is the permittivity of free space, e is the elementary charge and G is the gravitational constant, and where α is the fine-structure constant and m_P is the Planck mass.

Like the Planck scale, the Stoney scale functions as a symmetrical link between microcosmic and macrocosmic processes in general and yet it appears uniquely oriented towards the unification of electromagnetism and gravity . Thus for example whereas the Planck length is the mean square root of the reduced Compton wavelength and half the gravitational radius of any mass, the Stoney length is the mean square root of the 'electromagnetic radius' (see Classical electron radius) and half the gravitational radius of any mass, m:

where is the reduced Planck's constant and c is the speed of light. It should be noted however that these are only mathematical constructs since there must be some practical limit to how small a length can get. If the Stoney length is the minimum length then either a body's electromagnetic radius or its half gravitational radius is a physical impossibility, since one of these must be smaller than the Stoney length. If Planck length is the minimum then either a body's reduced Compton wavelength or its half gravitational radius is a physical impossibility since one of these must be smaller than the Planck length. Moreover, the Stoney length and Planck length cannot both be the minimum length.

According to contemporary convention, Planck scale is the scale of vacuum energy, below which space and time do not retain any physical significance. This prescription mandates a general neglect of the Stoney scale within the scientific community today. Previous to this mandate, Hermann Weyl made a notable attempt to construct a unified theory by associating a gravitational unit of charge with the Stoney length. Weyl's theory led to significant mathematical innovations but his theory is generally thought to lack physical significance.⁷⁸

Other

Stoney was the recipient of many honours and awards. Craters on Mars and the Moon are named in his honour. In 1899 he was the first recipient of the Boyle Medal, inaugurated by the Royal Dublin Society to recognise scientific research of exceptional merit by Irishmen. He was a member of the Royal Society for almost fifty years. He was a foreign member of the Academy of Science at Washington and of the Philosophical Society of America.¹

Stoney was the uncle of George FitzGerald, who was also a brilliant mathematical physicist. The two were in regular communication on scientific matters, and George went on to become a profesor of "natural and experimental philosophy" (i.e., physics) in Trinity College, Dublin. Stoney was also distantly related to Alan Turing.⁵

Stoney married his cousin and resided on Stoney Road, Dundrum, Dublin, which was named in his honour. They had two sons and three daughters. After Stoney died in London, his cremated ashes were buried in Dundrum, Dublin.

See also

• Planck units

References

Literature

• Alex Keller: The Infancy of Atomic Physics. Hercules in His Cradle, Oxford University 1983. ISBN 0-19-853904-5

External links

• Of the "Electron", or Atom of Electricity - by G. J. Stoney, Philosophical Magazine, Series 5, Volume 38, p. 418-420, October 1894